This invention relates generally to orthopedic plaster casts and, more particularly, to an improved plaster casting blank for use in preparing such casts.
Plaster casts such as those disclosed in U.S. Pat. Nos. 3,923,049 and 3,900,024 utilize a plurality of plaster splints disposed between two sheets of deformable water permeable material to form the casting blank. When wetted, the casting blank may be formed around a portion of a body and, upon curing of the plaster, a cast is thereby provided.
Casting blanks of the type described in the aforementioned patents represent a significant advance over the time consuming method of preparing casts by wrapping individually moistened plaster splints about the injured body portion. Because of the ease with which casting blanks may used to prepare casts, they have been widely used to prepare orthopedic casts. Such casting blanks are particularly well suited for use on an emergency basis, such as to immobilize broken bones at the scene of an accident or in a hospital emergency room prior to the final cast being applied.
It is desirable for the casting blanks of the type described above to have a rapid setting time to quickly immobilize the broken bone or other trauma to prevent further injury which might result from movement of the injured body portion. However, great care must be exercised in formulating the plaster within the blank to ensure that the amount of heat generated by the exothermic chemical reaction which leads to hardening of the plaster is less than that which would burn the patient's skin. The amount of heat generated by the chemical reaction generally increases as the setting rate of the plaster within the casting blank increases. As a result, casting blanks are often formulated to cure more slowly than would otherwise be desired to ensure that the temperatures generated remain within safe levels.
Another disadvantage of a rapid setting time for a casting blank is the decreased strength of the resulting cast. In general, the strength of the cast decreases as the setting time of the plaster decreases. Casts formed from rapidly setting plasters may lack the durability needed for other than short term use. Replacement of such casts is thus necessitated, with the attendant expense and discomfort for the patient. Moreover, conventional rapidly setting casting blanks may contribute to patient discomfort a the blanks have less opportunity to conform to the anatomical features of the underlying body part before hardening.
A need has thus developed for a rapidly setting casting blank which may be used to form a high strength cast to quickly immobilize an injury with reduced risk of burning the patient's skin and which provides greater patient comfort than achieved by conventional casting blanks.